/Engine/Plugins/Runtime/RigVM/Source/RigVM/Public/RigVMCore/RigVMStruct.h
Creates a new variable within the host of this VM
[FName](API\Runtime\Core\UObject\FName) AddExternalVariable ( const [FRigVMExternalVariable](API\Plugins\RigVM\RigVMCore\FRigVMExternalVariable) & InVariableToCreate, [FString](API\Runtime\Core\Containers\FString) InDefaultValue )